Photographic material as referred to herein is understood to be generally planar, may comprise film or paper, may produce a black-and-white or color image, and may be in a continuous web form or may comprise discrete sheets.
Silver halide photographic materials are well-known, and are processed to generate a silver or dye image via a development stage followed by a series of baths to stabilize and provide permanence to the image. Such baths convert and remove unwanted materials from the coated photographic layers which would either interfere with the quality of the final image or cause degradation of the image with time. In typical color systems the development stage is followed by a bleach stage to oxidize the developed silver to a form which can be dissolved by a fixing agent in the same or a separate bath. Such silver removal stages are then followed by a washing stage using water, or other wash solution, or a stabilization stage using a stabilizer solution. For convenience, this last-mentioned stage will hereinafter be referred to generically as "washing." Such stages remove residual chemicals and may also include conversion reactions between stabilizer solution components and materials within the coated layers. These stages are required to provide the required degree of permanence to the final image.
In many cases, particularly in small-scale "minilab" or "microlab" equipment, the wash stage is performed in a multi-tank arrangement. Usually the replenishment of this stage, which keeps the concentration of substances removed from the photographic material at a constant and sufficiently low level, is carried out by adding fresh wash solution to the final tank of the sequence and arranging over-flow from the final tank to flow into the previous tank and so on, the overflow from the first tank of this stage being then discarded as effluent. This is referred to as a "counter-current" mode. This arrangement allows significantly lower amounts of solution to be used compared with one or two tanks especially when these are replenished separately.
In a modern minilab a typical wash replenishment system might use around 200 cm.sup.3 of replenisher per m.sup.2 of sensitized material processed in a three or four-tank counter-current arrangement. The time the processed material spends in each tank is typically 20 to 25 seconds during which time an equilibrium is established between the concentration of substances in the coated material and the seasoned (steady-state) concentrations in the wash solution. The total time for this stage typically varies from 60 to over 100 seconds.
U.S. Pat. No. 5,541,700 discloses a photographic processing apparatus in which two processing tanks are provided in a single container that is divided into two by an air bubble at a dividing wall. Different processing solutions can then be introduced into each tank and maintained separate by the bubble whilst allowing the photographic material being processed to pass from one tank to the other through the bubble over the wall. This allows the number of containers to be reduced.